The invention relates generally to an apparatus for electrically stunning animals to be slaughtered in particular pigs. More specifically, the invention relates to apparatus comprising two endless conveyors. Which are operable to run parallel to each other and at a synchronized rate and are positioned to form a substantially V-shaped passageway therebetween. A pair of electrodes or sets of electrodes are provided and are adapted to engage the head of the animal to be stunned. The electrodes are further adapted to extend downwardly toward said V-shaped passageway in a spaced relationship to each other and are to clear said passageway.
One embodiment of an electrical stunning apparatus is disclosed in Applicant's prior application, Ser. No. 905,371, which is based upon Dutch patent application 77.05519 laid open to public inspection. In the above apparatus disclosed in applicant's prior application, two sets of electrodes are provided and are operable to pivot about horizontal shafts arranged above the conveyors. The electrodes are adapted to engage the head of the animal to be stunned and, upon engagement with the head of the animal, provide a jolt of current through the head of the animal, thus causing the stunning.
In stunning animals it is of utmost importance that the stunning is induced immediately by a jolt of intense current lasting a short time. A jolt of current of insufficient strength due to a bad contact, particularly if the electrical contact is intermittent or interrupted, may lead to a stress condition in the animal resulting in a change in the pH value of the meat to an undesired value. It may also cause muscular contractions, internal bleeding, and bone breakage which, in turn, results in a depreciation of the value of the meat.
Moreover, it is necessary that such apparatus provide high production levels for example on the order of 600 pigs per hour. Such production is possible if a short stunning time is utilized, provided that, an excellent contact is assured during this short time.
In the apparatus disclosed in applicant's prior application, the head of the animal engages the first electrode, or the first set of electrodes, which pass across the head of the animal. When the animal thereupon engages a second electrode, there will occur a passage of current capable of causing the stunning. To achieve a high production level, the conveyors move at such a rate that during the short period of current flow the animal will be displaced over a considerable distance, for example a distance of 30 cm (11.81 inches). The corresponding variable displacement of the electrodes with respect to the head of the animal causes the contact resistance between the electrode surface and the head of the animal to vary. The variations in the contact resistance may result in an unevenness in the stunning. In view of the length of the path along which the electrodes may pass across the head, it may be possible that the electrodes first engaging the head will engage the body too far behind the head during the period of current flow whereby the current may follow a less desired path during the period of current flow.
One feature of the present invention is that it improves upon this situation.